Method of incorporating ingredients in hydrophilic colloids

ABSTRACT

A COLOR-COUPLING OR MASK-FORMING COMPONENT IS INCORPORATED INTO A HYDROPHILIC COLLOID COMPOSITION AS A STABLE SOLUTION THEREIN BY MEANS OF A LOW BOILING WATER IMMISCIBLE ORGANIC SOLVENT IN WHICH THE COMPONENT IS DISSOLVED AND DISPERSED IN THE COLLOID COMPOSITION OR IN A PREPARATORY AQUEOUS LIQUID SUBSEQUENTLY ADMIXED WITH THE COLLOID COMPOSITION, THE ORGANIC SOLVENT BEING THEN REMOVED BY EVAPORATION WHEREBY THE COMPONENT IS CONTAINED IN SAID COLLOID OR THE PREPARATORY AQUEOUS LIQUID IN THE FORM OF A STABLE SOLUTION. THE MASK-FORMING OR COLORCOUPLING COMPONENT CARRIES AT LEAST ONE SULFO OR CARBOXYL GROUP WHICH IS IN SALT FORM OR IS CONVERTED INTO SALT FORM IN SITU BY CARRYING OUT THE DISPERSION STEP IN THE PRESENCE OF AN AMOUNT OF ALKALI SUFFICIENT TO NEUTRALIZE SUCH ACID GROUPS. A MINOR AMOUNT OF A WATER-MISCIBLE ORGANIC SOLVENT CAN ALSO BE PROVIDED TO FACILITATE THE DISSOLUTION OF THE COMPONENT IN THE WATER IMMISCIBLE SOLVENT AND BOTH SOLVENTS CAN BE REMOVED BY THE EVAPORATION. THE COLLOID COMPOSITION CAN BE A LIGHT-SENSITIVE SILVER HALIDE EMULSION DIRECTLY OR CAN BE ADDED AFTER ITS PREPARATION TO A LIGHTSENSITIVE SILVER HALIDE EMULSION.

United States Patent 3,752,672 METHOD OF INCORPORATING INGREDIENTS 1N HYDROPHILIC COLLOIDS Alfons Jozef De Pauw, Edegem, and Jan Albert Carpentier, Walem, Belgium, assignors to Gevaert-Agfa N.V., Mortsel, Belgium No Drawing. Continuation of abandoned application Ser. No. 766,937, Oct. 11, 1968. This application July 8,

1971, Ser. No. 160,959 Claims priority, application Great Britain, Oct. 11, 1967, 46,459/67 Int. Cl. G03c 1/10 US. Cl. 96-400 21 Claims ABSTRACT OF THE DISCLOSURE A color-coupling or mask-forming component is incorporated into a hydrophilic colloid composition as a stable solution therein by means of a low boiling water immiscible organic solvent in which the component is dissolved and dispersed in the colloid composition or in a preparatory aqueous liquid subsequently admixed with the colloid composition, the organic solvent being then removed by evaporation whereby the component is contained in said colloid or the preparatory aqueous liquid in the form of a stable solution. The mask-forming or colorcoupling component carries at least one sulfo or carboxyl group which is in salt form or is converted into salt form in situ by carrying out the dispersion step in the presence of an amount of alkali sufiicient to neutralize such acid groups. A minor amount of a water-miscible organic solvent can also be provided to facilitate the dissolution of the component in the water immiscible solvent and both solvents can be removed by the evaporation. The colloid composition can be a light-sensitive silver halide emulsion directly or can be added after its preparation to a lightsensitive silver halide emulsion.

This application is a continuation of application Ser. No. 766,937, filed on Oct. 11, 1968, and now abandoned.

The present invention is concerned with a method of incorporating colour couplers and mask-forming compounds in hydrophilic colloids more particularly with a method of preparing stable solutions of said colour couplers and mask-formers in water and aqueous hydrophilic colloid media.

By colour coupler is meant any compound which in silver halide photography couples with an oxidized aromatic primary amino colour developing agent to form a dye image. By mask-forming compound is meant a compound which oxidatively couples with a colour coupler in an oxidizing bleaching bath as for example described in United Kingdom patent specifications 880,862 and 975,- 932 to form a coloured mask image.

Some of the most useful types of colour couplers and mask-forming compounds for incorporating into photographic light-sensitive material are those which are provided in the course of their synthesis with one or more ballast groups, e.g. a long chain aliphatic group such as an alkyl or alkylene group of from 5 to 20 carbon atoms, which render them non-diifusible in hydrophilic colloid media. The presence of this ballast group imparts to the molecule a hydrophobic character. Therefore these nondifiusible colour couplers and mask-formers are also provided with one or more salt-forming groups i.e. carboxy and/or sulpho groups, which in the form of their alkali metal salts provide the ingredients with water-soluble groups of hydrophilic character so that said ingredients can still be incorporated from aqueous solutions in aqueous hydrophilic colloid compositions.

3,752,672 Patented Aug. 14, 1973 For the purpose of incorporating said components in aqueous hydrophilic colloid media said components are generally dissolved in a solution of an alkali metal hydroxide in water or a mixture of water and alcohol such as aqueous sodium hydroxide, alcoholic potassium hydroxide, etc., whereupon the resulting solution is incorporated into hydrophilic colloid compositions in liquid state, e.g. in aqueous solutions of hydrophilic colloids, in melted gels comprising hydrophilic colloids, etc.

However, the incorporation of these non-diifusible colour couplers and mask-formers containing salt-forming groups, into aqueous hydrophilic colloid compositions frequently still poses a number of difficulties. Indeed, certain of the above components carrying sulpho and/or carboxyl groups are not soluble enough, i.e. in the concentration desired, in said alkaline solutions while others crystallize after some time in said solutions or give rise to flocculation when incorporating the ingredient solution in the aqueous hydrophilic colloid medium. Moreover, some compounds are soluble only in highly alkaline solutions which are too basic for use as such in conventional light-sensitive silver halide material, where approximately neutral solutions are most desirable; when highly alkaline solutions are used the hydrophilic colloid composition should be reacidified afterwards whereby flocculation might occur and whereby inorganic salts are formed which must be washed out.

Another difficulty attendant to this procedure of incorporating colour couplers and mask-formers into hydrophilic colloid media is the frequent use of alcohol for facilitating the dissolution of the ingredient in the aqueous alkaline solution; indeed, it is known that the alcohol generally gives rise to an elevation of the viscosity of the hydrophilic colloid medium. In most cases there is an eX- tended but varying holding time between the addition of the ingredient solution to the hydrophilic colloid composition and the actual application of said composition to the film base, or other hydrophilic colloid layer which has been coated previously. It is very important that during this holding time the viscosity be held constant because .with the currently used coating techniques any variation or drift in viscosity will result in difierent coating thicknesses. Thus, with constant coating speed, lower viscosity win produce a thinner layer while higher viscosity will result in a layer thicker than desired.

A method has now been found for preparing stable aqueous solutions of colour couplers and mask-formers carrying sulpho and/or carboxyll groups with which the above difficulties are not encountered. This method is particularly suitable for preparing aqueous solutions of nonditlusible colour couplers and mask-formers carrying sulpho and/or carboxyl groups which are intended to be incorporated into liquid hydrophilic colloid media for preparing a photographic material.

In accordance with the invention a method is provided of forming a stable aqueous solution of a colour coupler or mask-former carrying one or more sulpho groups and/ or carboxyl groups, which method comprises intimately blending said colour coupler or mask-former simultaneously or successively with at least one substantially water-immiscible solvent for said compound and with water, said blending taking place in the presence of alkali e.g. an alkali metal or ammonium hydroxide or carbonate and preferably also in the presence of a wetting agent, removing substantially all of the said solvent(s) from the dispersion in water of the organic solution of said colour coupler or mask-former forming thereby an aqueous solution of the said colour coupler or mask-former.

In the above process of the invention for preparing stable solutions of colour couplers or mask-formers in water it is possible to leave out the alkali; for that purpose, there is started from the said compounds in salt form and not in their acid form, e.g. the compounds are used in the form of an alkali metal carboxylate, ammonium carboxylate, alkali metal sulphonate or ammonium sulphonate.

By the wording blending said colour coupler or maskformer simultaneously or successively with a substantially water-immiscible solvent and with water it is meant to embrace the following alternatives: first, that the colour coupler or mask-former is dispersed in a mixture of water and the said solvent, and second, that the colour coupler or mask-former is dissolved in the said solvent and the solution obtained is then dispersed in water.

From an aqueous solution of a colour coupler or maskformer formed in the above way the said mask-former or colour coupler can be successfully incorporated without special stirring technique, e.g. by gentle mixing, and without giving rise to flocculation into a hydrophilic colloid medium, e.g. an aqueous gelatin solution, a gelled gelatino silver halide emulsion, etc.

The present invention therefore also includes methods of incorporating a colour coupler or mask-former carrying at least one sulpho group and/or carboxyl group into a hydrophilic colloid composition, more particularly a photographic hydrophilic colloid composition, by the steps of intimately blending said colour coupler or mask-former simultaneously or successively with at least one substantially water-immiscible solvent for said component and with water, said blending taking place in the presence of alkali and preferably also in the presence of a wetting agent, removing substantially all of the said solvent(s) and admixing the aqueous solution formed with the hydrophilic colloid composition.

As an alternative to the above method for incorporating an organic component as defined above in a hydrophilic colloid composition, the dispersion in water of the organic solution of the colour coupler or mask-former formed as described above is admxed with the said hydrophilic colloid medium before removal of the said solvent(s); when the solvent(s) is (are) removed from the aqueous hydrophilic colloid composition the colour coupler or mask-former is gradually transferred from the solvent phase to the aqueous phase forming thereby a stable solution of the said mask-former or colour coupler in the said colloid composition. This alternative method can still be simplified by leaving out the step of admixing the solution of colour coupler or mask-former in the substantially water-immiscible solvent with water which means that the said component solution can be successfully admixed with an aqueous hydrophilic colloid composition whereupon the solvent is removed and a solution of mask-former or colour coupler in hydrophilic colloid is formed.

According to a preferred embodiment a colour coupler or mask-former carrying one or more carboxyl and/r sulpho groups is incorporated into a hydrophilic colloid composition by the steps of dissolving said colour coupler or mask-former in a substantially water-immiscible solvent in the presence of alkali, dispersing the solution formed in water preferably in the presence of a wetting agent, removing substantially all of the said solvent during and/or after dispersing said organic solution in water and admixing the aqueous solution formed with a hydrophilic photographic colloid composition. As an alternative, the said colour coupler or mask former is dissolved in the said solvent in the absence of alkali while the solution formed is dispersed in water in the presence of alkali.

A second preferred embodiment of the method of incorporating colour couplers or mask-formers into hydrophilic colloid compositions according to the invention differs from the first preferred embodiment in that the said component carrying one or more sulpho and/or carboxyl groups is intimately blended with a mixture of substantially water-immiscible solvent, water and alkali, preferably in the presence of a wetting agent, whereupon the substantially water-immiscible solvent is substantially removed thus forming a stable aqueous solution of the said component and the said aqueous solution is admixed with the said hydrophilic colloid composition.

According to a third favoured embodiment the colour coupler or mask-former is incorporated into a hydrophilic colloid composition by the steps of dissolving said mask-former or colour coupler carrying one or more sulpho and/or carboxyl groups in a substantially water-immiscible solvent in the presence of alkali, dispersing the solution formed preferably in the presence of a wetting agent, in an aqueous hydrophilic colloid composition and removing substantially all of the said solvent leaving thereby the colour coupler or mask-former dissolved in the aqueous hydrophilic colloid composition.

As already remarked above, the addition of alkali can be left out in the three embodiments just given by using the colour coupler or mask-former in its salt form e.g. alkali metal salt form.

In accordance with the present invention it is possible to form stable solutions in water or in aqueous hydrophilic colloid compositions of colour couplers and mask formers carrying at least one sulpho group and/or carboxyl group that are otherwise not easily soluble in water or said aqueous hydrophilic colloid media or not to as high a concentration. Thus in accordance with the invention concentrated solutions of colour couplers and mask-formers in water or aqueous hydrophilic colloid media can be prepared with a minimum of water. Moreover, in the method of the invention no excess of alkali is required so that practically neutral solutions can be formed. In these solutions the ingredients do not crystallize upon storage. Moreover when incorporated from said solutions into hydrophilic colloid media the colour couplers and mask-formers do not give rise to flocculation and the hydrophilic colloid composition need not be acidified since the amount of alkali used can be limited to that necessary to neutralize the salt-forming groups of the component.

Thus, although the invention is applicable and advantageous for all kinds of nonpolymeric colour couplers and mask-formers as defined above including those which in the form of alkali metal and ammonium salts readily dissolve in Water in the concentration required, difficultly water soluble colour couplers, and mask-formers, i.e., those which in their alkali metal and ammonium salts form do not readily dissolve in water or crystallize upon storage when dissolved in water in the amount required or give rise to flocculation when incorporated from said solution into a hydrophilic colloid medium, as well as colour couplers and mask-formers which require excessively high alkalinity for being dissolved in water, lend themselves particularly to the process of the invention. That such a result would be obtained is rather startling since it would be expected that upon removal of said solvent, precipitation (crystallization or flocculation) of the colour coupler or mask-former would occur. However, examination with high power optical equipment of the aqueous solutions or hydrophilic colloid compositions into which the colour coupler or mask-former have been incorporated according to the invention failed to reveal the presence of discrete particles of the ingredient.

When incorporating colour couplers or mask-formers into hydrophilic colloid media from aqueous solutions prepared according to the method of the invention no alcohol need be used as is otherwise frequently the case for facilitating the dissolution of photographic ingredients in aqueous alkaline solutions so that a drift in viscosity in said media can be avoided whereby the coating thickness of said colloid compositions or other colloid compositions to which those first mentioned are added will not vary in the course of time. Moreover, in accordance with the method(s) of the invention it is possible to obtain an intimate mixing in the desired and exact ratio of colour couplers and mask-formers which in the course of the photographic process should react with each other. Indeed, it is possible to prepare according to the invention a solution in water or hydrophilic colloid of colour couplers and mask-formers at the same time. By preparing a solution in Water or hydrophilic colloid of the colour coupler and mask-forming compound in accordance with the present invention and incorporating said solution into a lightsensitive silver halide emulsion, both compounds are intimately mixed with each other and are present in the exact and always the same ratio throughout the emulsion layer.

In the preparation of solutions of colour couplers or mask-formers in water or hydrophilic colloid media in accordance with the invention usually a minimum of water is used, in order to obtain solutions as concentrated as possible which is particularly suitable for storing purposes. This minimum varies of course with each individual component and can be determined by trial. The amount of substantially water-immiscible solvent used is dependent on the solubility of the particular compound therein: it can vary within very wide limits but is also preferably restricted to a minimum.

In accordance with the invention it is possible to incorporate colour couplers and mask-formers directly into the colloid coating composition of the layer into which said component is intended to be present. However, it is also possible to create stocks of the concentrated aqueous solutions of colour couplers and mask-formers or of the solutions of colour couplers and mask-formers in aqueous hydrophilic colloid compositions (in gelled state) obtained in accordance with the invention. Parts of these stocks are then used whenever the occasion requires. Although it would be possible to create stocks of the aqueous solutions of colour couplers or mask-formers obtained in ac-- cordance with the invention it is preferred to mix said aqueous solution with an aqueous solution or melted gel of photographic colloid and to create stocks of the resultant colloid composition (preferably in gelled state), parts of which are then incorporated at the appropriate moment into the colloid coating composition of the layer of the photographic material into which the colour coupler or mask-former must the present. Of course, when the aqueous solution of colour coupler or mask-former is incorporated into a mere aqueous solution or melted gel of photographic colloid for storing purposes the concentration of the component in the resultant gel is preferably as high as possible.

The said colloid coating compositions for forming a layer of a photographic material may of course contain in addition to the colloid carrier all sorts of other ingredients.

The amount of stored aqueous solution or colloid composition to be added to the colloid coating composition of the photographic layer is such that the colour coupler and/or mask-former is present in the resulting layer in the desired concentration. This amount is naturally dependent on the concentration of said component in said aqueous solution or colloid composition.

The use of a preformed aqueous solution of the colour coupler or mask-former or of a preformed colloid composition obtained as referred to above offers an excellent reproducibility since it is possible to incorporate the colour coupler or mask-former into the photographic light-sensitive emulsion or other colloid composition for coating a photographic layer, always with the same concentration.

The removal of the substantially water-immiscible sol- 'vent may be achieved for instance Iby evaporation, if necessary, e.g. for accelerating the removal, by applying reduced pressure and/or moderate heating, by steamdistillation (particularly when high boiling substantially water-immiscible solvents are used), etc.

The substantially water-immiscible solvents preferably have a solubility in Water of at most 25% by weight at room temperature. Substantially water-immiscible solvents having a solubility in water comprised between 2 and 10% by weight at room temperature are even the more favoured. Moreover, said solvents preferably have a boiling point of at most 130 C. and a sufficiently high vapour pressure so that they can still readily be removed from the aqueous dispersion by applying a vacuum of 500 to 10 mm. Hg at a temperature of 25 to C.

Examples of suitable substantially water-immiscible solvents for use according to the present invention are: methylene chloride, methyl formate, ethyl formate, n-butylformate, methyl acetate, ethyl acetate, n-propyl acetate, isopropyl acetate, butyl acetate, methyl propionate, ethyl propionate, carbon tetrachloride, sym. tetrachloroethane, 1,1,2-trichloroethane, 1,2-dichloropropane, chloroform, n-butyl alcohol, methyl ethyl ketone, diethyl ketone, methyl-n-propyl ketone, diisopropyl ether, cyclohexane, methyl cyclohexane, benzene, toluene, nitromethane, etc.

In order to facilitate dissolving of the colour coupler or mask-former it may be interesting in some cases to use in conjunction with the substantially water-immiscible solvent a solvent which is miscible with water in all proportions. Of course, said water-miscible solvent should be completely miscible with the substantially water-immiscible solvent. The boiling point of the water-miscible solvent is not critical but is also preferably lower than C. Indeed, When the water-miscible solvents have a sufficiently high vapour pressure they can be rapidly removed together with the substantially water-immiscible solvent, if necessary by applying a vacuum of 500 to 10 mg. Hg at a temperature of 25-80 C.

In cases Where aqueous solutions of colour couplers or mask-formers are prepared according to the method of the invention and in conjunction with the substantially water-immiscible solvents completely water-miscible solvents are used having a vapour pressure not sufficiently low to be removed together with the substantially Waterimmiscible solvents, said Water-miscible solvents can be best removed afterwards, unless they are photographically inert, viz by Washing the chilled and thereby gelled colloid composition to which the aqueous ingredient solution is added.

Examples of water-miscible solvents that are particularly suitable for use in conjunction with the substantially water-immiscible solvents are methanol, ethanol, isopropyl alcohol, dimethyl sulphoxide, tetrahydrofuran, N- methyl-Z-pyrrolidone, dioxan, dimethyl formarnide, dimethoxyethane, formadie, ethylene glycol, acetonitrile, acetone, butyrolactone, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diacetone alcohol, tetrahydrothiophene-l,l-dioxide. Evidently, mixtures of said solvents may be used too.

The solvent partners in the mixture of solvents employed according to the present invention for dissolving the colour couplers or mask-former are chosen in such a way that the said component dissolves completely with the concentration required.

The method for preparing aqueous solutions of colour couplers or mask-formers carrying at least one sulpho and/or carboxyl group is preferably carried out in the presence of one or more wetting agents. In the preferred embodiment of the method of the invention where the component in a first step is dissolved in the substantially water-immiscible solvent and the solution obtained is dispersed in a second step in water said wetting agents can be used in the said first and/ or the said second step.

Thus, the wetting agent can be added already at the step of dissolving the colour coupler or mask-former in the organic solvent(s) whereby it is possible to eliminate the use of a wetting agent at the stage of dispersing the organic solution in water or two different wetting agents can be used, one in each step. The wetting agents used may be of the ionic, non-ionic or amphoteric type. Examples of suitable ionic wetting agents are: the sodium salt of oleyltauride, sodium stearate, heptadecenylbenzimidazole sulphonic acid sodium salt, sodium sulphonates of higher aliphatic alcohols, e.g. Z-methylhexanol sodium sulphonate; sodium diiso-octyl-sulphosuccinate, sodium dodecyl sulphate and tetradecyl benzene sulphonic acid sodium salt. Examples of suitable non-ionic emulsifying agents are: saponine, condensation products of alkyl phenols and ethylene oxide, e.g. octylphenyl polyglycol ether, isononylphenoxypoly(ethylen-oxy)ethanol and polyethylene glycol oleate.

A survey of emulsifying agents and wetting agents, representatives of which can be applied according to the present invention are described by Gerhard Gawalek Waschund Netzmittel, Akademieverlag Berlin (1962).

Although in applying the method according to the present invention for incorporating colour couplers or maskformers in hydrophilic colloid media, the use of gelatin as hydrophilic colloid is favoured, other water-soluble colloidal materials or mixtures of them can be used too, e.g. colloidal albumin, zein, casein, a cellulose derivative such as carboxymethyl cellulose, a synthetic hydrophilic colloid such as polyvinyl alcohol, poly-N-vinyl pyrrolidone, etc.

The following examples illustrate the present invention.

EXAMPLE 1 7.09 g. of colour coupler having the following structural formula:

were admixed with a mixture comprising 90 ml. of water, ml. of 10% aqueous saponin and 18 ml. of ethyl acetate. The mixture was stirred and heated at 55 C. whereby the colour coupler dissolved gradually. Then the ethyl acetate was substantially removed by evaporation under reduced pressure of about 400 mm. Hg at 55 C. A clear, stable, aqueous solution of colour coupler was formed.

This aqueous solution could be readily admixed at a temperature of 38 C. with a blue-sensitive silver halide emulsion ready for coating and no crystallization occurred. The said aqueous solution could also be added to a mere aqueous solution of gelatin or melted gelatin gel whereupon the composition formed could be stored for weeks in gelled state and then, after having been remelted incorporated into a said silver halide emulsion ready for coating.

The same result was attained when using 18 ml. of methylene chloride as organic solvent instead of ethyl acetate.

NaOsS EXAMPLE 2 Example 1 was repeated with the difference, however, that for the formation of the stable aqueous solution of colour coupler, the said colour coupler was now first dissolved at 60 C. in 30 ml. of ethyl acetate or 30 ml. of methylene chloride and the solution formed was then dispersed in 100 ml. of water in the presence of 10 ml. of 10% aqueous saponin.

EXAMPLE 3 3.94 g. of colour coupler having the following structural formula:

were dissolved at 55 C. in 30 m1. of ethyl acetate in the presence of 5 ml. of 2 N sodium hydroxide. With stirring the solution formed was dispersed in ml. of water comprising 10 ml. of dispersing agent with formula:

whereupon the ethyl acetate was substantially removed by evaporation under reduced pressure of about 400- mm. Hg at 50-55 C. A clear aqueous solution of colour coupler was formed which could be readily admixed with a green-sensitized gelatino silver halide emulsion ready for coating. The said solution could also be added to a mere aqueous solution of gelatin or melted gelatin gel where upon the composition formed could be stored for weeks in gelled state and then after having been remelted, incorporated into such an emulsion at the appropriate moment.

EXAMPLE 4 Example 3 was repeated with the difference however, that, for the formation of the stable aqueous solution of the colour coupler, the said colour coupler was now dispersed at 55 C., with stirring in a mixture of 100 ml. of water, 5 ml. of 2 N potassium hydroxide, 18 ml. of ethyl acetate and 10 ml. of the said dispersing agent, whereupon the ethyl acetate was removed.

EXAMPLE 5 3 g. of colour coupler having the following structural formula:

were dissolved at 50 C. in 18.5 ml. of ethyl acetate in the presence of 2.75 ml. of 2 N potassium hydroxide. The solution formed was then dispersed in 50 ml. of water in the presence of 10 ml. of a 10% aqueous solution of saponin. The ethyl acetate was removed by evaporation under reduced pressure of about 400 mm. Hg at 50 C. until the total weight of the resulting clear aqueous solution was 50 g. This solution had a pH of 5.1.

The solution was admixed with 50 g. of a 6% aqueous solution of gelatin, which could then be stored in gelled state for several weeks without showing flocculation or crystallization of the colour coupler.

The gel was finally mixed with a green-sensitized lightsensitive gelatino silver halide emulsion and the colour emulsion formed was coated in the usual way as an emulsion layer of a multilayer photographic colour material.

EXAMPLE 6 I 4.75 g. of colour coupler having the following structural formula:

were dissolved at 60 C. in 45 ml. of ethyl acetate in the presence of 5 ml. of 2 N sodium hydroxide and 5 ml. of

a 10% aqueous solution of the dispersing agent of the formula:

NaOaS H N NaOsS The solution formed was dispersed in 95 ml. of water whereupon the ethyl acetate was distilled off under reduced pressure of about 400 mm. Hg at 50-55 C. A clear aqueous solution of colour coupler was obtained, which could be further used for incorporating said colour coupler into a light-sensitive silver halide emulsion in a same manner as described in Example 5.

EXAMPLE 7 6.4 g. of colour coupler having the following structural formula:

CHI I C O-NH-H were dissolved at 60 C. in 30 ml. of ethyl acetate, whereupon the solution formed was dispersed in 100 ml. of distilled water in the presence of 10 ml. of a 10% aqueous solution of saponin. After the removal of the ethyl acetate by evaporation under reduced pressure at 50-55 C. a clear, stable aqueous solution of the color coupler was obtained.

The same result was attained with chloroform as organic solvent for the colour coupler instead of ethyl acetate.

The stable aqueous solutions formed could be further used for incorporating said colour coupler into a redsensitized silver halide emulsion in a similar manner as described in Example 5.

EXAMPLE 8 Example 7 was repeated with the difference however, that the solution of colour coupler in ethyl acetate was dispersed in 100 ml. of a aqueous solution of gelatin in the presence of ml. of a 10% aqueous solution of saponin. After removal of, the ethyl acetate by evaporation under reduced pressure at 50-55 C. a clear stable solution of colour coupler in aqueous gelatin was obtained.

The gelatin solution comprising colour coupler was admixed with a red-sensitized gelatin silver halide emulsion and the colour emulsion formed was coated in the usual way as an emulsion layer of a multilayer photographic colour material.

EXAMPLE 9 4.82 g. of colour coupler having the following structural formula:

10 EXAMPLE 10 Example 9 was repeated with the difference, however, that for the formation of the stable aqueous solution of colour coupler, 4.82 g. of the said colour coupler was now dispersed in a mixture containing 100 ml. of water, 5 ml. of 2 N potassium hydroxide, 20 ml. of ethyl acetate and 10 ml. of a 10% aqueous solution of saponin whereupon the ethyl acetate was removed.

EXAMPLE 11 0.586 g. of colour coupler having the following structural formula:

0(CH C Ha NBC 0 CHZU 0Q was admixed at C. with 5.5 ml. of water, 0.5 ml. of 2 N sodium hydroxide, 1.5 ml. of ethyl acetate and 0.5 ml. of a 10% aqueous solution of saponin. Then the ethyl acetate was substantially removed under reduced pressure of 400 mm. Hg at 50-55" C.

The aqueous solution of colour coupler formed was then admixed with a conventional blue-sensitive silver halide emulsion. The emulsion obtained is called emulsion A.

An emulsion B was prepared as follows:

0.586 g. of the above colour coupler was dissolved at 55 C. in 4.5 ml. of ethanol in the presence of 1 ml. of 2 N sodium hydroxide whereupon 2 ml. of water were added. The solution formed was admixed with a same amount of the said blue-sensitive silver halide emulsion whereupon the excess of alkali was neutralized by means of N acetic acid. In this way emulsion B was formed.

Now, emulsions A and B were compared as to their viscosity in the following simple way: I

A calibrated pipet with two marks corresponding with 10 ml., with filled with emulsion taking care that no air bubbles were formed. The pipet was positioned vertically and the flow out time in seconds was measured by means of a chronometer. It took 42 seconds for emulsion B to cover the distance from one mark to the other whereas it took only 26 seconds for emulsions A to cover the same distance.

From this example it clearly appears that emulsion A is much less viscous than emulsion B.

What is claimed is:

1. Method of incorporating into a hydrophilic colloid composition a non-polymeric non-diffusing color-coupling or mask-forming component diflicultly soluble in water and carrying on the molecule thereof a hydrophobic group and at least one sulfo group or carboxyl group in salt form, by the steps comprising:

dissolving said component in an organic solvent therefor which is substantially immiscible with water and has a boiling point not higher than about 130 C., admixing and dispersing the solvent with said com- CHr-CO OH were dissolved at 55 C. in '30 ml. of ethyl acetate in the presence of 5 ml. of 2 N potassium hydroxide. The solution formed was dispersed in 100 ml. of water in the presence of 5 ml. of an 80% aqueous solution of sodium dodecyl sulphate whereupon the ethyl acetate was substantially removed by evaporation under reduced pressure of about 400 mm. Hg at 50-55 C.

A clear stable aqueous solution of colour coupler was obtained, which could be further used for incorporating said colour coupler into a light-sensitive silver halide emulsion in a similar way as described in Example 5.

4. The method of claim 3 wherein the amount of said alkali is that required to neutralize the acid groups of said component.

5. The method of claim 1 wherein a minor amount of a water-miscible organic solvent is added to said waterirnmiscible solvent for dissolving said component.

6. The method of claim 5 wherein said water-miscible solvent also has a boiling point not higher than about 130 C. and is removed -by evaporation with said waterimmiscible solvent.

7. The method of claim 1 wherein said colloid com position is a light-sensitive silver halide colloid composition.

8. The method of claim 1 wherein said colloid composition containing said component is added to a lightsensitive silver halide composition.

9. The method of claim 1 wherein said Water-immiscible organic solvent is ethyl acetate or methylene chloride.

10. Method of incorporating into a hydrophilic colloid composition a non-polymeric non-diffusing color-coupling or mask-forming component difiicultly soluble in water and carrying on the molecule thereof a hydrophobic group and at least one sulfo group or carboxyl group in salt form by the steps comprising dissolving said component in an organic solvent therefor which is substantially immiscible with water and has a boiling point not higher than about 130 C., dispersing said.

solvent containing said component in an aqueous liquid miscible with said colloid composition, admixing said aqueous liquid containing said component in said colloid composition, and substantially removing by evaporation said organic solvent, whereby a stable solution of said component in said colloid composition is produced.

11. The method of claim wherein said organic solvent is substantially removed by evaporation from said aqueous liquid before the same is admixed with said colloid composition.

12. The method of claim 10 wherein said organic solvent is substantially removed by evaporation from the admixture of aqueous liquid and colloid composition.

13. The method of claim 10 wherein said dissolving and dispersing steps are carried out substantially concurrently.

14. The method of claim 10 wherein said dispersing step takes place in the presence of a wetting agent.

15. The method of claim 10 wherein the salt form of said component is formed in situ by dissolving said component in free acid form in said solvent in the presence of alkali.

16. The method of claim 15 wherein the amount of said alkali is that required to neutralize the acid groups of said component.

17. The method of claim 10 wherein a minor amount of a water-miscible organic solvent is added to said water-immiscible solvent for dissolving said component.

18. The method of claim 10 wherein said water-miscible solvent has a boiling point not higher than about C. and is removed by evaporating with said water-immiscible solvent.

19. The method of claim 10 wherein said colloid composition is a light-sensitive silver halide colloid composition.

20. The method of claim 10 wherein said colloid composition containing said component is added to a lightsensitive silver halide colloid composition.

21. The method of claim 10 wherein said water-immiscible organic solvent is ethyl acetate or methylene chloride.

References Cited UNITED STATES PATENTS 3,451,820 6/1969 Umberger et al. 96-100 3,416,923 12/1968 Van Campen et al. 96-82 3,469,987 9/1969 Owens et al. 96-82 FOREIGN PATENTS 749,225 5/ 1957 Great Britain 96-100 1,038,039 8/1966 Great Britain 96-100 1,099,416 1/1968 Great Britain 96-100 844,865 12/ 1956 Great Britain 96-100 912,969 9/ 1960 Great Britain 96-100 937,387 5/1961 Great Britain 96-100 WILLIAM D. MARTIN, Primary Examiner M. SOFOCLEOUS, Assistant Examiner U.S. Cl. X.R. 96-9 

